<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script type="text/javascript">
			 let _a = null;
			 Object.defineProperty(this, 'a', {
				 get() {
					 return ++_a;
				 }
			 })
			console.log(a === 1 && a === 2 && a === 3);
		</script>
	</body>
</html>
